1. Field of the Invention
This invention relates to voltage control circuits. Particularly disclosed herein are voltage doubler circuits for use with gas lasers and, more particularly, for use with transversely excited atmospheric pressure (TEA) lasers.
2. Prior Art
Many voltage control circuits, including voltage doublers, have been disclosed in the past. Such circuits have been designed to use either DC or AC power supplies and, in the AC supply case, charge energy storage elements (e.g. capacitors) during only one-half cycle or the full cycle.
However, a simple high voltage multiplier circuit, and particularly a doubler, which can be easily adapted to supply substantial DC voltage to a load only when switched on has not heretofore been disclosed. The present invention affords the characteristics listed immediately above and is particularly useful in supplying gas laser discharge voltages.
A popular prior art voltage doubler for gas lasers is shown in FIG. 1, i.e. the Marx generator. In Marx generator 10 the DC supply KVDC.sub.IN charges capacitors 12 and 14 (which have the same capacitance), with the same polarity, as shown. After capacitors 12 and 14 are fully charged, when spark gap 16 fires, capacitors 12 and 14 are momentarily placed in series thus applying the full voltage stored in capacitors 12 and 14 to the load, a TEA laser. Since two capacitors 12 and 14 are provided, twice the voltage which can be stored on either capacitor is applied to the TEA laser.
However, prior to firing spark gap 16, when capacitor 14 is fully charged, the full input voltage KVDC.sub.IN which is equal to one-half of device 10's output voltage is applied to the TEA laser. Generally the maximum output voltage of device 10 is just sufficient to discharge the TEA laser. In that case, one-half the output voltage is approximately one-half the laser discharge voltage. Application of one-half the laser discharge voltage to the TEA laser prior to the seleced firing of the laser leads to undesirable corona and gas discharge effects inside the laser. Spark gap 16 must withstand one-half the full laser discharge voltage in Marx generator 10 for proper operation.
The Marx generator multiplies an output voltage and its spark gap must withstand half the output voltage, but it supplies one-half the full DC output voltage to the laser prior to pulsing the laser with the full output voltage. Further, in the Marx generator, no ground connection is made directly to the spark gap. Such a connection is desirable in high voltage applications.